Prescribing for Astigmatism

Give Your Low Astigmats the Best Vision Possible

BY VISHAKHA THAKRAR, OD, FAAO

How many of you regularly reach for a toric lens for patients who have astigmatism equal to or less than 1.00D? I bet the vast majority of you try a spherical lens first before attempting a toric fit. I too am guilty of this. However, I now think that it is time to rethink this strategy.

Try Some Newer Designs

Toric lenses used to be more difficult to fit and more uncomfortable compared to spherical lenses. This has changed with newer toric designs. Today's toric lenses are almost as easy to fit as spherical designs, and the comfort is now comparable.

So why aren't we offering toric lenses to our patients more readily? Are we hesitant to offer a more expensive option if we feel that they “really don't need it”? Is 20/20− or 20/25 vision acceptable when we know that they can be corrected to a sharper 20/20? The following case demonstrates the importance of offering toric lenses to patients who have low astigmatism.

In Sharper Focus

A 39-year-old white female presented to my office for contact lens fitting. She had been wearing monthly disposable spherical silicone hydrogel lenses OD and OS for the past two years. She reported that the lenses were comfortable so she had been throwing them away every two months. Distance visual acuities were 20/20 OD and 20/20 OS. The manifest refraction was OD −2.25 −0.25 x 157 20/20 and OS −2.50 −0.75 x 010 20/20. Slit lamp examination revealed grade 2 papillae in the superior and inferior tarsal plates OD and OS and grade 2 diffuse bulbar hyperemia OD and OS.

We refit her into two-week disposable spherical lenses OD and OS and re-educated her about the importance of not overwearing her lenses. After trying the lenses, she mentioned that family members had commented for years that she had been squinting, but she felt that her vision was fine. The visual acuity was still 20/20 OD and OS.

Based on her comments, I performed a sphero-cylindrical over-refraction, which was OD +0.25 −1.00 x 160 20/20 and OS +0.25 −1.00 x 010 20/20. There appeared to be some induced astigmatism in the right eye and uncorrected astigmatism in the left eye. Subsequently, we refit her into two-week toric lenses to improve her visual acuity. The patient instantly felt like she could see more clearly. When she returned for her two-week follow up, she was subjectively much happier with her vision and the lenses were very comfortable. Because she appreciated the improvement in vision, paying a slight premium on the lenses was not an issue.

Give Patients the Best

As eyecare practitioners, we have a responsibility to provide the best vision possible for our patients. This case demonstrates that even a patient who sees very well can benefit from astigmatism correction. It's important to remember that when astigmatic patients are fit with spherical contact lenses, it may be worthwhile to do a sphero-cylindrical over-refraction to see whether the visual improvement is appreciable. Toric contact lenses have the potential to sharpen vision beyond what spherical contact lenses can mask. CLS

Dr. Thakrar has a specialty contact lens practice and is a clinical optometrist at TLC Laser Eye Center in Mississauga, Ontario. She is also a professional affairs consultant to Vistakon. You can reach her at thakrarv@gmail.com.